This invention relates to a method and apparatus for permanently implanting leads adjacent the heart, plus fixation devices for holding implanted leads in desired positions anywhere in the body. The term "leads" is intended to also include other implantable fixtures besides electrical leads, such as fluid conduits, reservoirs and the like.
It is well-known in the field of cardiology that ventricular fibrillation can be effectively treated by the application of electrical shocks to the heart. Such defibrillation may be achieved by the application of electrical paddles to the chest of the patient or directly to the heart tissue, if the chest is open during surgery.
More recent improvements have lead to the development of implantable defibrillators, which monitor the heart for arrhythmias and automatically initiate defibrillation when fibrillation occurs. Such devices often incorporate electrodes that are located on the epicardium or parietal pericardium, being connected to a defibrillation unit by means of a lead.
However, major surgery is generally necessary to implant and affix present defibrillator lead systems into their desired position. For example, a median sternotomy or lateral thoracotomy may be required. Such procedures can be very traumatic to the patient, and may have adverse side effects such as surgical complications, morbidity, or even mortality. Candidates for such a procedure thus may include only those persons for whom the potential benefits outweigh the significant risks. Because of the significant surgical risks of the present lead systems, many patients who might otherwise benefit from the use of an implantable defibrillator are excluded.
The issue of fixation of the lead into a desired position can be important for any implantable device, but it is especially important for defibrillator leads, since the electrodes of the typical pair of defibrillator leads present cannot be allowed to touch each other. When implanting paddle electrodes via sternotomy or thoracotomy, there is adequate access of the leads and surrounding tissues to suture the edges of the leads to those tissues to fixate the leads in place. However, in the case of a deployable lead that has been placed through a small incision, or a paddle electrode placed through a small incision using a limited surgery technique, suturing by hand is not possible due to the lack of access and the lack of visibility. A deployable lead is a lead that is inserted into its position in a transversely collapsed configuration, with the electrodes being then allowed to expand outwardly into a new, laterally expanded configuration which is typically larger than the incision providing entry of the lead into its desired position.
Another difficulty involved in fixating leads to the epicardium, when compared to fixating leads to the endocardium, relates to the lack of trabeculae for engagement with tines, and also the presence of coronary blood vessels that must be avoided if one attempts to use screws or hooks that penetrate the tissue.
By this invention, a lead is preferably attached to the parietal pericardium, and not the epicardium. Thus there is practically no possibility of rupturing coronary vessels or of tearing myocardium. Also, no endoscope, rigid or flexible, is required in order to provide good fixation of the lead to the parietal pericardium. It is possible to crimp a fixation device as described herein so that no sharp edges of the device are exposed to tissue. Likewise, the fixation device may be visible on x-ray and fluoroscopy, for effective observation both during implantation and afterward. Likewise, fixation devices as described herein may be attached firmly, yet relatively atraumatically, since only fibrous tissue is penetrated and gripped. Thus there is essentially no possibility of puncturing the pleura, and the pericardium remains intact.
The lead may be removed by coring the parietal pericardium, or the lead may be removed by snapping its fixation device apart, while the lead is held by snapping the fixation device together. Also, the fixation device for the lead can be made so unobtrusive that an abandoned fastener can be left attached to the parietal pericardium and a new one placed, if desired.
Thus, the invention of this application exhibits significant advantages over prior art methods for implanting leads, particularly adjacent the heart, as shown for example in Chin et al. U.S. Pat. No. 4,865,037 or Person U.S. Pat. No. 3,999,555, for example.